I would add that you set your recording format in the audio hardware normally. You use the driver applications that came with your hardware to set record format, then you simple select the device or interfaces inside Vegas to record. That goes for the stock onboard audio interfaces also. If that makes any sense.

You should be able to search this forum, or other posts on Magix's forum for people trying to use pro audio interfaces with Vegas. I know there have been several posts over the years on this topic.